FIG. 1 is a rear, side perspective view of a rear portion of a bicycle helmet showing my new design;

FIG. 2 is a left side elevational view thereof, the right side is symmetrical;

FIG. 3 is a top plan view thereof;

FIG. 4 is a bottom plan view thereof;

FIG. 5 is a front elevational view thereof; and,

FIG. 6 is a rear elevational view thereof.

Any broken line illustration in the drawing disclosure of the bicycle helmet and rear portion thereof is shown for the purpose of illustrating environment and is not part of the design sought to be patented.